The delivery system of useful materials such as skin care or cosmetic materials or drugs into the body by coating the skin with the materials or applying a pack or patch to the skin enjoys the advantage of allowing the continuous transport of the materials, generating no pain, and being convenient for use.
However, because the stratum corneum, which is the outermost epidermal layer of skin, is 10 μm to 60 μm thick, it serves as a barrier to the penetration of foreign matter into the body, thus a delivery system using coating or patches is very poor in absorption efficiency. Particularly, when the materials to be delivered are hydrophilic or have a large molecular weight, their absorption into the body becomes poorer.
Injection is an effective method to deliver a useful material into the body. Having dimensions of millimeters for diameter and centimeters for length, however, an injection needle stimulates many pain receptors, causing a significant pain in a subject to which the injection needle is applied. In addition, injection should be performed in hospitals or specialized skin care institutes, and cannot be easily used at home.
To overcome the drawback of conventional injection, micro-needles were developed to have a diameter of tens to hundreds μm and a length of hundreds to thousands μm. The micro-needles form micropores in the stratum corneum so that they allow materials, even though hydrophilic or large, to be readily absorbed into the skin or delivered into the body through the skin.
In addition, when applied to the site that is pierced with the conventional micro-needles, useful materials are absorbed or delivered into the body at better rates. Further, since micro-needles are too short to reach the dermis layer where nerve cells are distributed, no pain is generated upon the application of micro-needles. Even though micro-needles pierce into the dermis layer, they are smaller in diameter and length and stimulate fewer pain receptors than conventional injection needles so that the subject feels only minor pain.
WO 02/047555 discloses a device for treating the skin of a subject, including a head defining a convex head surface, and a plurality of spaced pins set in the head and protruding a predetermined distance from the head surface, and a method of treating the skin of a subject by pressing the device onto the skin of the subject with sufficient force for the pins to pierce the epidermis of the subject, leaving minute clefts in the epidermis.
U.S. Pat. No. 5,487,726 describes a percutaneous vaccine applicator system adapted to apply a vaccine to the skin and to form minute clefts in the stratum corneum.
According to WO 02/047555 and U.S. Pat. No. 5,487,726, however, it is inconvenient for the subject to use the device or the system because the dermal application of drugs and the percutaneous formation of minute clefts are conducted separately.
U.S. Pat. No. 6,603,998 discloses a method for delivery molecules into cells by coating a micro-needle-type electrode with a molecule to be delivered, and applying the electrode to the skin.
U.S. Pat. No. 6,132,755 discloses a system for the actively controlled transcorneal delivery of a medicament, in which a drug container provided with micropins is designed to allow active substance to pass through capillary openings of the micropins into the subject with the aid of a pump.
U.S. Patent Application No 2005/0251088 discloses a method for the delivery of a medicament in which the medicament stored in pores of a porous needle is percutaneously delivered when the porous needle forms minute clefts in the epidermis.
U.S. Pat. No. 3,964,482 discloses a drug delivery device, comprising a puncturing projection communicating with a drug reservoir wherein when the puncturing projection is applied to the stratum corneum of the epidermis, the drug is percutaneously administered into the skin by diffusion.
However, all of U.S. Pat. Nos. 6,603,998, 6,132,755, and 3,964,482, and U.S. Patent Application No. 2005/0251088 require additional devices for the delivery of a material of interest.
An alternative method of facilitating the transdermal delivery of a skin care cosmetic material is to use a stratum corneum-abrading cosmetic before application of the skin care cosmetic to the skin. For this, the stratum corneum may be generally removed with a scrubbing agent. The scrubbing agent must be washed off before a skin care cosmetic material is applied to the skin. Further, caution must be taken to avoid the entry of a scrubbing agent into the eye. If present in the eye, the scrubbing agent is difficult to remove. In addition to causing the sensation of foreign matter, the presence of scrubbing agent in the eye may abrade the corneum when the eye is rubbed.
Korean Patent No. 10-1206985 discloses a cosmetic composition for massaging the skin, comprising sugar scrubbers admixed with a non-aqueous cosmetic material. The cosmetic composition exhibits functions of moisturizing the skin, facilitating blood circulation, and removing dermal dead cells and corneal layers.
However, the sugar scrubbers of Korean Patent No. 10-1206985 have a general morphology of 8 or more faces, with blunt edges and large angles between the faces, and thus their scrubbing effect is not significant.
Leading to the present invention, intensive and thorough research of the present inventors into the delivery of skin care cosmetic substance or medicament resulted in the finding that tetrahedral or pyramidal micro-needles containing a dermal cosmetic material or a drug can be used as scrubbers to readily induce the percutaneous delivery of the dermal cosmetic material or the drug.